Control device



POUNDS PER sq m (GAGE) a) Aug; 15, 1944. c, G. KRONMILLER 2,355,872

CONTROL DEVI CE Filed June 17, 1942 50 25 Q 25 SO I00 I I I15 200 250 215 TEM PERATQRE (F) INVENTOR. Carl G. Krona Y1111m il 5 4. W

ATTORNEY.

fig. 2

Patented Aug. 15, 1944 UNITED STATES: PATENT OFFICE 2355.812 oomnon DEVICE Cari G. Kronmiller, Minneapolis, Minn, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation oi Delaware Application June 17, 1942, Serial'No. 447,346

17 Claims. (Cl. 0043) The present invention relates to a control device, and more particularly to such a device comprising novel safety features and means for lowering operating pressures in such structure.

In control devices in electrical circuits. for deenergizing the same upon the occurrence of an undesirable condition, it is common practice to rupture due to high pressure or deterioration, the

switch will be left in the on position and no protection is afforded thereby.

An object of thiminvention, therefore, is to employ in a temperature responsive device an actuating pressure medium which operates at relatively low pressures tothereby reduce the danger oi bursting 0! parts and to obviate the necessity for bulky mechanism.

Another object oi my invention is to provide a temperature responsive device subject to an actuating pressure medium having a relatively low boiling point so that the expansive force of the medium in a gaseous form may be used in the operating range of the device and the pressure medium further providingsubstantiai pressure even at very low temperatures so as to thereby prevent a shutdown of the system due to lack oi pressure or expansion of the actuating medium at the low temperatures.

Another object is to provide auxiliary linkage to positively open the limit switch it parts of said device should burst or deteriorate so as to cause the actuating hold to leak out of the actuating parts and thereby reduce the pressure force 01' the actuating medium.

A iurther object is ,to provide supplemental means to cause operation of the auxiliary link-- use to open the switch as a result of an undesirable extreme condition at the pressure generating capsule accompained by a failure of the normal high pressure cutout portion of the device to operate properly due to binding or failure of parts thereof.

It is also an object of my invention to provide a novel double spring tension means whereby the temperature at which the auxiliary linkage will open the limit switch may be adjusted with greater exactitude.

Another object resides in the combination of functions of parts set forth in the preceding objects to provide a, control device having optimum safety characteristics.

Other objects reside in the novel arrangement of parts of the present structure and will be in part obvious or pointed out in the accompanying specification and claims.

In the drawing.

Figure l is an elevational view of a preferred form of my invention with some of the actuating parts shown in section, and,

Figure 2 is a, pressure-temperature chart of one fluid which may be used with my structure.

Referring now to Figure 1, the reference char-- acter 10 represents a switch casing having a mercury switch it therein which has a suitable mercury fill 82 for bridging electrodes l3 and H. The mercury switch ii is carried by a clip i5 which is suitably secured to an arm it. The

arm ii is in turn secured to'a pivot it which is formed soas to extend horizontally out from the rear of the casing iii. The arm it has a pin l8 at its lower end by which the member it is rotated.

An actuating member 2!) is pivoted upon a knife edge H. The member 20 is biased so as to rotate in a clockwise direction by a pair of adjustment springs 25 and 26, which are suitably secured to upstanding ears 2? and 28, respectiveiy, upon the base 2% oi the actuating memher it The spring 25 is the main adjustment spring and is stronger than the spring 25. A suitable adjustment screw 3!! is secured to the upper part of the spring 25 and when rotated is adapted to either. increase or decrease the tension therein. A suitable guide and indicator 3! extends exteriorly to the casing i0 and cooperates with a scale plate 32 to indicate the setting of the main spring 25. to give a finer adjustment and is a weaker spring than the spring 25. An adjustment screw 35 is secured to the upper part of the spring 28 and is adapted upon rotation to either increase or decrease the tension therein. An arm 36 extends exteriorly of the casing in and cooperates with the scale plate 32 to indicate the adjustment oi the spring 25. From the foregoing it is seen that an adjustment is provided for giving a first rough adjustment through the relatively heavy spring 25 and for thereafter adjusting the temperature value at which the switch will operate to a nicety by a weaker spring 26.

The spring 26 is adapted I The base portion 2! of the switch actuating member is adapted to b moved between upper and lower ears of a stop member 40. This stop member is provided so that the mercury switch II will not be rocked to an extreme position but will be kept within a certain desired angle of operation. A leveling means is shown as mounted freely upon a post 46 and cooperates at its lower end with a mark 41 upon the casing ill to indicate when the entire device is leveled properly so that the switch II will operate properly within this predetermined limit of movement.

The actuating member 20 is adapted to be rocked by a pressure responsive means generally indicated by the reference character 50. The pressure responsive member 80 comprises a casing 51 which is suitably secured to the casing II by a flange 52. Within the housing BI is a bellows 53 which is secured at its upper portion to a mounting plate II and at its lower end to a movable head 55. The head 55 is suitably secured to a stem 56 which is fixed to a cone member 51 that cooperates with a crater 58 in the actuating member 20. Pressure for actuating the bellows 53 is generated in a capsule 80 which may bepartially filled with a suitable volatile fluid, such as propane. Adjustment means for determining the initial pressure to be exerted in order to cause movement of the bellows 53 is determined by a spring BI and an adjusting nut 02 which is screw-threadedly mounted into the upper assembly plate 83 for the pressure motor structure 50. By rotating the screw 62, the spring 6| is more or less tensioned to determine the proper operating pressures for the bellows Bl.

All of the structure discussed above in connection with my novel switch mechanism is made of light material. By such structure the cost of production is kept low, together with ease of forming the parts. To make it possible to use smaller parts in my device, I have used what may be termed a fade-out fill for the pressure generating means which actuates the pressure motor 50. By using such a fill, my structure can be used at relatively high temperatures while still not creating correspondingly high pressures. For example, in Figure 2, I have shown a chart disclosing the temperature and pressure characteristics of the fluid propane upon its boiling. It will be understood that the pressures to be referred to hereinaftercan be varied without departing from the spirit of my invention. Also it will be understood that certain variations in pressure will not seriously affect the operation of my (device as these variations may be compensated for by my adjustment spring structure.

Referring now more in detail to Figure 2, I have shown on the lower left-hand corner of a temperature pressure chart the curve for saturated propane. It will be noted that the saturated fiuid'will exert different pressures at different temperaturesand that the rate of pressure increase rises at a relatively great rate upon the increase in temperature. In my novel switch structure I use just enough propane fluid so that it will boil out completely and change into a gas in the neighborhood of 20 F., as indicated on the chart. After this fluid has changed completely into a gas, the pressure and temperature .curve will take the form of substantially a shown as a straight line extending ofl toward the upper right-hand corner of the chart.

It may be assumed that my novel control structure is to be used to control the limit in the bonnet of a hot air furnace. In such structure, the bulb 00 will be placed in the bonnet and the casing ll may be suitably secured at any desirable place. for example, upon a control panel adjacent the burner or at some other position as desired by the user thereof. It is desirable in such furnaces that the temperature in the bonnet thereof shall .not exceed a certain predetermined value, for

example, In other words, if the temperature increases beyond this degree in a warm air furnace, it will cause an uncomfortable condition for the occupants of the dwelling. Hence, when the temperature remains below that value in my novel structure, it is desirable for the mercury switch I i to be in such position that the electrodes l3 and H are bridged by the mercury l2. Hence, the springs 2| and 20 will be so adjusted that the bellows 63 will not rock the actuating member 20 until such time as the temperature approaches this limit temperature. When this temperature is reached, it is desirable to have the switch ll rock to its other position in which the mercury I! does not bridge electrodes I3 and I4.'

Rocking of the switch H and opening of the switch will then result in de-energization of the burner or the fuel supply means or some damper means to cut off the supply of heat. Thereafter the temperature will drop and result in rocking the mercury switch back again to close the switch.

Assume now that a portion of my switch actuating structure should begin to leak for some reason, such as the breaking loose of a connection or some deterioration of the parts thereof. Under these circumstances, the same condition would prevail as under low temperature conditions at the capsule N and hence the mercury switch will be in the on position. However, at this time, with a leak, the pressure within the bellows N will be reduced substantially to atmospheric pressure. It will be noted upon refcream: to the chart disclosed in Figure 2 that my arrangement has been adapted to operate at its limit control setting of 150 F. slightly in excess of 50 lbs. above atmospheric pressure. Now, if the pressure acting on the bellows ll is reduced to atmospheric pressure, there is substantially no pressure exerted upon the bellows It other than the internal stress due to tension in the bellows itself. The spring 0| therefore will urge the plate II toward its lowermost position and thus stretch out the bellows II.

.I have shown an auxiliary linkage for actuating the mercury switch H to open position in the event of occurrence of an abnormally low pressure aflecting the bellows II. This means is shown as an L-shaped bell crank ll mounted on a pivot 10a and having an abutting end II which is adapted to engage a plate I! carried upon the actuating stem 56 when said plate moves below a predetermined normal range of movement. When the end II is eng sed by the plate [2, the bell crank II will be rotated in a counter-clockwise direction. At the upper and of thebell crank 10, alink I4 is secured to a pivot Ii. The other end of the link ll connects to a pin 10 which is secured to the switch carrying arm I. Hence, by reason of engagement of the end II with the abutment plate I! and the consequent rotation in counter-clockwise directionofthebellcrankli,thelink14willbemoved towards the left. Such movement will move the switch carrying member IE to the left and cause the mercury within the tube H to move to the right-hand end thereof and break the circuit through the electrodes l3 and I4.

During operation discussed above, the switch actuating member will be in the position shown in the drawing. Hence, to permit movement of the switch mounting arm 16, a strain re- 8! having an car 82 to which a spring 83 connects with an ear 84 upon the actuating arm 20. The spring 83 biases the arm 8| of thestrain release mechanism 80 clockwise toward the right, and a pin 85 mounted on the member 20 limits the movement of the arm 8| under the tension of the spring 83. However, when the auxiliary switch actuating mechanism comes into operation due to an abnormally low pressure, the arm Bi of the strain release mechanism 80 is pivoted toward the left by the switch actuating pin l8 under force of the bell crank lever Hi, thereby permitting the switch I l to be rotated to its open circuit position. The spring 6| for adjusting the bellows 53 is stronger than the spring 83 in the strain release mechanism 80, so that the spring 6! will overcome'the spring 83 to actuate the mercury switch II when the base member 29 being limited to the stop member 40 is shown in Figure 1.

In the event that some of the structure may bind .or fail to operate due to breakage of parts or due to a slow leak in the bellows, capsule or connecting conduit, I have disclosed additional means forcausing the auxiliary switch actuating means to be brought into operation. This additional means is shown as a fusible plug 60a in the temperature responsive capsule 60. The fusible plug may be so selected that it will melt at some predetermined extreme temperature condition. When placed in the bonnet of a furnace such as described above, it may be desirable to have the plug melt at 250. Hence, "if the pressure actuated limit switch is adapted to control at 150, the plug 60a, will not normally be brought into operation and the switch structure will be actuated normally by the bellows 53 and the pressure generated by the gas in the capsule 60 through the normal actuating link 20. If, however, no leak occurs in the bellows or in the connections thereto and some of the actuating linkage should fail, the increase in pressure affecting the bellows 53 would not cause the mercury switch to be actuated to open position. Under such circumstances, the heater would not be turned off and the temperature would rise excessively to an undesirable value. At, this time, in order to protect the property from damage which might result from fire, it is desirable to shut down the system. Hence, when the temperature rises to a value of, for example, 250, the fusible plug 60a. will melt out of the capsule 60 and permit the actuating medium therein to decrease in pressure, substantially to atmos pheric pressure. At this time, the auxiliary actuating means which rotates the switch upon the occurrence of low pressure will be brought into operation to cause the mercury switch II to be rocked in a clockwise direction to unbridge the electrodes l3 and M. It is seen, therefore, that this structure gives an additional safety feature which brings into play my auxiliary switch actuating means to cause opening of the switch under extreme temperature conditions.

The plug 60a. is also useful in preventing unsafe failure of my device due to the occurrence of a slow leak therein. If such a slow leak should occur, the pressure existing within the capsule 60 might not correctly indicate the temperature adjacent the capsule. If the leak were slow, the pressure within the chamber formed by the bellows 53 and the housing 5| might indicate that the temperature adjacent the capsule 60 was in the safe range, when actually it was unsafely high. Under such conditions, an unsafely high temperature might exist adjacent the capsule 60 without causing operation of the switch H to open position. The plug 60a is provided to prevent such an unsafe operation of my device. If the temperature adjacent the capsule 60 exceeds 250, for example, the plug 60a melts, thereby immediately reducing the pressure inside the capsule to atmospheric pressure, whereupon the spring 6! pushes the stem downwardly and causes opening of the switch H through the bell crank lever 10.

From the foregoing disclosure of a preferred embodiment of my invention, undoubtedly others skilled in the art will conceive many modifications and variations thereof. Also, other uses will be found for my control switch. For this reason, I wish not to be limited only to that form shown and. described, but by the spirit and scope of the appended claims and the prior art.

I claim as my invention:

1. In a control device comprising a switch movable between first and second positions by an actuator, the combination of pressure responsive means for moving said actuator, spring means for adjusting the pressure value at which switch actuation will occur, means for varying the pressure acting on said pressure responsive means in response to a controlling condition, a member moved by said pressure responsive means when said pressure is below a desired value, connecting means between said member and said switch, and strain release means upon said actuator, said member when moved causing actuation of said switch and said strain release means thereby preventing stress from being placed upon said actuator.

2. In a temperature responsive pressure operated device, a pivot, a mercury switch mounted for rocking therearound, a pressure motor comprising a bellows, a spring biasing said bellows in one direction, a pressure generating capsule partially filled with a volatile fluid acting on said bellows in the opposit direction, said fluid being completely gasified at normal operating pressures for said device so said pressures will be .substantially pressures resulting from temperature variations affecting a. gas, and first and second actuating linkages actuated by said motor selectively at different pressures for actuating said control means, said first linkage moving said control means between active and inactive positions under normal pressur conditions, and said second linkage moving said control means from active to inactive positions under subnormal pressure conditions.

3. In a device of the character described, comprising in combination, control means operable between first and second positions, temperature responsive variable pressure means, an actuating lever operably connected to the said temperature responsive variable pressure means for positioning the said control means in the first of its positions at a predetermined high pressure, another actuating lever operably connected to the said temperature responsive variable pressure means for positioning the said control means in said first of its positions at a predetermined low pressure, and automatic biasing means operably connected to said temperature responsive variable pressur means in such a manner as to return the said control means from said first or its positions aforesaid upon a pressure exerted by the said temperature responsive variable pressure means having a value between that of the aforesaid predetermined high and low pressures.

4. In a device of the class described, comprising in combination, a circuit control means operable between closed and open positions, a pivot, a lever pivotally mounted on the said pivot and the said lever for actuating the said control means, temperature responsive expansion means operably connected to the said lever at one side of the said pivot so as to actuate the said lever, a plurality of adjustment springs secured to the said lever at the opposite side of the said pivot so as to resist the expansive force of the said expansion means, the said adjustment springs connected at different points of the said lever and one 01' the said expansion springs having a greater tension force than another of the said adjustment springs, separate adjustment means for each of the said springs and the said spring of lesser tension being so arranged that adjustment thereof will render a finer tension adjustment for the said lever than adjustment of the said spring of greater tension so as to more accurately regulate the actuation of the said control means, and means operably connected to the said springs for indicating the adjustment thereof.

5. In a temperature responsive pressure operated device, a pivot, a mercury switch mounted for rocking therearound, a pressure motor comprising a bellows, a spring biasing said bellows in one direction, a pressure generating capsule partially filled with a volatile fluid acting on said bellows in the opposite direction, said fiuid being completely gasifled at normal operating pressures for said device so said pressures will be substantially pressures resulting from temperature variations affecting a gas; a first lever acted on by said motor for rocking said switch, spring means secured to said first lever for adjusting the pressure value at which said switch will be rocked thereby; said first lever rocking said switch to an inactive position when the pressure increases, and said spring means operating said switch to an active position when th pressure decreases, a strain release associated with said first lever, and a second lever acted on by said motor for operating said switch when the pressure diminishes to a predetermined low value, said second lever overcoming said strain release and rocking said switch to its inactive position.

means secured to said first lever for adjusting the pressure value at which said switch will be rocked thereby; said first lever rocking said switch to an inactive position when the pressure increases, and said spring means operating said switch to an active position when the pressure decreases, a strain release associated with said first lever, a second lever acted on by said motor for operating said switch when the pressure diminishes to a predetermined low value, said second lever overcoming said strain release and rocking said switch to its inactive position, and supplemental means for causing operation or said second lever upon the occurrence of an undesirable temperature condition.

7. A control device, comprising in combination, a closed chamber having a first portion thereof exposed to a variable temperature and a second portion movable in accordance with the 'difference between the internal and external pressures acting thereon, a body of fiuid'within said chamber whose pressure lies within a normal range greater than atmospheric when said variable temperature lies within a corresponding normal range, spring means associated with said second portion to bias it against movement by the normal difference in the pressures acting thereon and to maintain said second portion in a normal position when said pressure lies within said normal range, control means movable between an active position and a safe position, means biasing said control means to its active position, a member attached to the second portion of said chamber for movement therewith, a pair of actuating linkages, each linkage including an element positioned in the path of said member to be engaged thereby upon a movement thereof in one of two opposite directions from said normal position, each linkage also including means efiective upon further movement of said element in said one direction as an incident to a change in said pressure from said normal range to move said control means against its bias to its safe position, and a fusible plug in said first portion of said chamber efiective upon an increase in said temperature to a value substantially above said corresponding normal range to open said chamber to the atmosphere, thereby in- 6. In a temperature responsive pressure opersuring operation of said control means to its safe position.

8. A control device, comprising in combination, a closed chamber having a first portion thereof exposed to a variable temperature and a second portion movable in accordance with the dinerence between the internal and external pressures acting thereon, a body of fiuid within said chamber whose pressure lies within a normal range substantially different from atmospheric pressure when said variable temperature lies within a corresponding normal range, spring means associated with said second portion to bias it against movement by the normal difference in the pressures acting thereon, and to maintain said second portion in a normal position when said pressure lies within said normal range, control means movable between an active position and a safe position, means biasing said control means to its active position, a member attached to the second portion of said chamber for movement therewith. actuating means for said control means including an element positioned in the path otsaid member and operable thereby upon a. decrease in the difierence between said internal and external pressures to move said control means against its bias to its safe position, and a fusible plug in said first portion or said chamber elective upon an increase in said temperature to a value substantially above said corresponding normal range to open said chamber to the atmosphere, thereby insuring operation of. said control means to its safe position.

9. A control device, comprising in combination, a closed chamber having a first portioncthereof exposed to a variable temperature and a second portion movable in accordance with the difference between the internal and external pressures acting thereon, a body of fluid within said chamber whose pressure lies within a normal range greater than atmospheric when said variable temperature lies within'a corresponding normal range, spring means associated with said second portion to bias it against movement by the normal difference in the pressures acting thereon and to maintain said second portion in a normal position when said pressure lies within said normal range, control means movable between an active position and a safe position, means biasing said control means to its active position, a member attached to the second portion of said chamber for movement therewith, and a pair oi actuating linkages, each linkage including an element positioned in the path of said member to be engaged thereby upon a movement thereof in one of two opposite directions, each linkage also includin means effective upon further movement of said element in said one direction to move said control means against its bias to its safe position.

10. A control .device, comprisingin combination, control means operable between an active position and a safe position, means biasing said control means to said active position, a, movable member having a normal position, means responsive to a condition indicative of the need for operation of said control means for moving said member in opposite directions from said normal position in accordance with the variations of said condition from a normal range of values, and a pair of actuating linkages, each linkage including an element positioned in the path of said member to be engaged thereby upon a movement thereof in one of said directions, each linkage also including means effective upon further movement of said element in said one direction to move said. control means against its bias to its safe position.

11. A control device, comprising in combination, control means operable between an active position and a safe position, means biasing said control means to said active position, a movable member having a normal position, means responsive to a condition indicative of the need for operation of said control means for movnormal position in accordance with the variatlons of said condition from a normal a e of values, a pair of actuating linkages, each linkage including an element positioned in the path or said member to be engaged thereby upon a movement thereof in one of said directions, each linkage also including means effective upon further movement of said element in said one direction to move said control means against its bias to its inactive position, and strain release means connecting said control means with one of said elements to relieve strain on said linkages when said control means is operated by the other of said elements.

12. A control device, comprising in combination, a closed chamber having a first portion thereof exposed to a variable temperature and a difference between the internal and external pressures acting thereon, a body of fluid within said chamber whose pressure lies within 2. normal range greater than atmospheric when said variable temperature lies within a corresponding normal range, spring means associated with said second portion to bias it against movement by the normal difference in the pressures acting thereon, and to maintain said second portion in a normal position when said pressure lies within said normal range, control means movable between an active 'position and a safe position, means biasing said control means to its active position, a member attached to the second por- :tion of said chamber for movement therewith, and a pair of actuating linkages, each linkage including an element positioned inthe path of said member to be engaged thereby upon a movement thereof in one of two opposite directions from said normal position, and means effective u on further movement of said element in said one direction as an incident to a change in said pressure from said normal range to move said control means against its bias to it's safe position, said biasing means being eiiective upon restoration of said pressure to its normal range to return said control means to said active position.

13. A control device, comprising in combination, control means operable between an active position and a safe position, means biasing said control means to said active position, a movable member having a normal position, means responsive to a condition indicative of the need for operation of said control means for moving said member in opposite directions from said normal position in accordance with the variations of said condition from a normal range of values, and a pair of actuating linkages, each linkage including. an element positioned in the path of said member to be engaged thereby upon a movement thereof in one of said directions, each linkage also including means eiiective upon further movement of said element in said one direction to move said control means against its bias to its inactive position, said biasing means being effective upon restoration of said condition to its normal range to return said control means to said active position.

14. Ina control device, comprising in combination, control means operable between first and second positions, a pressure, movable member having a normal position, means responsive to a condition indicative of the need for operation of said control means for moving said member in two directions from said normal position in accordance with the variations of said condition from a normal range of values, first and second actuating linkages, the first linkage being engaged by said member upon movement oi? the said member in one of the said directions for moving the control means to the first or its positions, and the second linkage being engaged by the said member upon' movement of said member in the second of said directions for also moving the control means to said first of its positions, and a plurality of adjustment springs connected at different points to said first linkage means for resisting the, movement or the movable member in one of its directions.

15. A control device, comprising in combination, control means operable between a first position and second position, a movable member having a normal position, means responsive to a condition indicative of the need for operation or second portion'movablein accordance with the said control means tor moving said member in first and second directions from its normal position in'accordance with the variations of the condition from a normal range of values, a first linkage means, asecond linkage means, the responsive means under a change in the condition above the normal range 0! values moving the movable member in one of said directions engaging the first linkage means thereby actuat-- ing the first linkage means for moving the control means to the first of its positions, and the responsive means under a change of the condition below the normal range of values moving the movable member in the second direction engaging the second linkage means thereby actuating the second linkage means for moving the control means to the said first of its positions.

16. A control device, comprising in combination, control means operable between first and seconds positions, means biasing said control means to the first of its positions, a movable member having a normal position, means responsive to a condition indicative oi the need for operation of said control means for moving said member in first andsecond directions from said normal position in accordance with the variations of said condition from a normal range oi values, first linkage means, means, the responsive means under a change in the condition above the normal range of values moving the said movable member in the first direction engaging the first linkage means thereby actuating the first linkage means for moving the control means to the second of its positions, and the responsive means under a change in the condition below the normal range of values moving the movable member in the second direction engaging the second linkage means thereby actusting the second linkage means for moving the control means to said second of its positions, and said biasing means being eiiective upon restoration 01 said condition to its normal range to return said control to the first of its positions.

17. A control device, comprising in combination, control means operable between first and second positions, means biasing said control means to the first of its positions, a movable member having a normal position, means responsive to a condition indicative of the need for operation 0! said control means for moving said control member in first and second directions from said normal position in accordance with the variations 0! said condition irom a normal range of values, first, linkage means, second linkage means, the responsive means under a change in the condition above the normal range of values second linkage moving the movable member in the first direction to engage the first linkage means thereby actuating the first linkage means for moving the control member to the second of its positions, and the responsive means under a change in the condition below the normal range of values moving the movable member in the second direction to engage the second linkage means thereby actuating the second linkage means for moving the control means to the second of its positions, a strain release means connecting said control means to the first linkage to relieve the strain on said linkage and said control means when the control means is actuated by the second linkage means, and said biasing means effective upon restoration of said condition to its normal range of values to return said control means to the first of its positions.

CARL G. KRONMIILER 

